Dyn's conjecture on the regularity of generalized Daubechies wavelets

Let n2n\ge 2 and let Λn={λ0,,λn1}\Lambda_n=\{\lambda_0,\ldots,\lambda_{n-1}\} be an arbitrary set of real numbers. Let ψΛn\psi^{\Lambda_n} be the generalized Daubechies wavelet associated with Λn\Lambda_n, and let φn\varphi_n be the classical stationary nnth Daubechies refinable function. Write αψΛn\alpha_{\psi^{\Lambda_n}} and αφn\alpha_{\varphi_n} for their Hölder exponents. Dyn's conjecture. The Hölder regularity of every generalized Daubechies type wavelet is equal to the Hölder regularity of the corresponding classical Daubechies wavelet, equivalently

αψΛn=αφn.\alpha_{\psi^{\Lambda_n}}=\alpha_{\varphi_n}.

The generalized wavelets arise from non-stationary subdivision schemes reproducing exponential polynomials with spectrum Λn\Lambda_n, while the classical wavelets arise from the limiting stationary masks. The paper proves this conjecture using its regularity theorem under the stated convergence and approximate sum-rule assumptions.

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Primary source

Maria Charina, Costanza Conti, Nicola Guglielmi and Vladimir Protasov, “Regularity of Non-Stationary Multivariate Subdivision”, arXiv:1406.7131 (2015).

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